The invention relates to a compartment for powder coating workpieces.
Such compartments have been known and used for a long time. The interior of the compartments is limited by sidewalls, end walls at both ends, a compartment floor, and a compartment roof which is divided by a longitudinal gap. Usually the workpieces are moved through this longitudinal gap by means of a conveyor. To permit such conveyance, the compartment has an aperture for workpieces at least in its upstream end wall. Often a manual coating station is provided next to the compartment at the side thereof and adjacent the upstream end wall. There is an opening in the sidewall of the compartment that belongs to this manual coating station. Through the opening an operator can prime areas of the workpiece which are difficult to coat or need a prime coat by manipulating a hand spray gun inside the compartment and upstream of the automatic coating, in conveying direction of the workpieces. If desired or required, a second manual coating station is provided, likewise laterally of the compartment, downstream of the automatic coating of the workpieces, in conveying direction of the workpieces. Any insufficiently coated and/or complicated areas of the workpieces thus may be recoated manually, as needed, inside the compartment by a person acting from this other manual coating station.
The free space is limited when manipulating the hand spray guns since the manual coating must be accomplished in the interior of the compartment through openings in the compartment.
During the coating operation powder particles may escape to the outside through the rather great openings at the manual coating stations, causing harm to the environment and loss of powder. This disadvantageous effect might be compensated by reinforcing the vacuum which prevails inside the compartment. That would bring about a corresponding increase of the suction effect and alter the flow conditions inside the compartment to such a degree that the coating quality would suffer.
Moreover, lighting conditions inside the compartment are not sufficient to allow accurate manual working. For this reason lamps are provided in the known compartment at the location of the manual coating stations to illuminate the workpieces at the locations of the respective manual coating stations, more specifically in the sidewall next to the openings provided for the manual coating stations so that the workpieces are illuminated from the front. In operation these lamps become contaminated very fast by deposits of excess powder.
It is an object of the invention to design a compartment of the kind defined initially such that the escape of powder particles into the environment of the compartment is reduced while unobstructed, high-quality manual coating still can be achieved economically, i.e. especially, without increasing the suction effect.
Other than in the prior art, the workpieces are pre- and/or re-coated outside of the compartment at a manual coating station which, according to the invention, is located upstream or downstream of the compartment in conveying direction. Thus the person doing the manual coating inherently is offered practically unlimited free space for careful manual coating, as would not be available even with very large lateral openings for manual coating in the state of the art. This is possible without any extra expenditure while, at the same time, achieving superior manual coating quality.
Daylight or the workshop lighting which is installed anyway may be sufficient to illuminate the portions to be coated. In addition, lamps may be mounted at the outside of the compartment for illumination of the coating places. In this manner the unavoidable illumination in the interior of the compartment may be realized in the form of lighting fixtures in the ceiling, in other words at a location which is not sensitive to contamination.
The preferred arrangement of the respective manual coating station near the aperture which always is kept open during operation makes sure that practically none of the powder sprayed when manually coating workpieces gets lost to the environment. The negative pressure inside the compartment has the effect of any excess powder which does not reach the workpiece being sucked through the aperture into the compartment.
Further advantageous modifications of the invention are protected by the other subclaims.